The present invention related generally to ram air inlet structures for providing coolant air to heat generating components within a vehicle, and more particularly to a variable area inlet structure for thermal control on heat generating components within a vehicle configured principally for reducing vehicle drag and thermal cycling of the components so cooled.
Aircraft, automobiles and other vehicle types use ambient air as a heat sink for cooling heat generating components within a vehicle. Most vehicles rely on ram air for forced convection cooling with fans to augment the ram air at low speeds. Currently, vehicles use fixed area inlets to conduct ram air into compartments containing heat generating components. A characteristic of fixed area inlet configurations is that the ducted air speed generally increases with vehicle speed and higher speeds generally improve the rate of convective heat transfer from the heat generating component to the ducted air. Low ducted air temperatures also improve the rate of heat transfer.
The combination of vehicle speed, ambient air temperature, and inlet characteristics present trade-offs for fixed area inlet configurations. However, fixed area inlets cannot be optimal for all vehicle speed and ambient temperature operating conditions. As a consequence, fixed area inlets are usually overdesigned in order to accommodate severe environmental conditions (i.e., northern winter air temperatures and southern summer air temperatures), which results in increased drag losses and reduced vehicle performance and efficiency. A substantial portion of the drag coefficient on an aircraft or an automobile may be attributable internal cooling air flow. Fixed area inlets may also cause undesirable thermal cycling of the cooled component.
The invention solves or substantially reduces in critical importance problems with conventional vehicle structures incorporating ram air cooling inlet structures as just suggested by providing a variable area inlet structure for thermal control on heat generating components within a vehicle comprising a variable area inlet device in the form of a butterfly valve, damper, shutter or similar structure, a temperature sensor in thermal contact with the heat generating component, and a programmable controller and an actuator in the form of a stepper motor or the like, responsive to signals from the temperature sensor, for controlling the area of the ram air inlet and, correspondingly, regulating the temperature of the component. The invention may be used in any vehicle using ram air coolant, such as aircraft, unmanned aerial vehicles, automobiles and other ground based vehicles and watercraft. Heat generating components which may be typically cooled include electronic equipment and engine parts.
It is therefore a principal object of the invention to provide a variable area inlet structure for conducting ram air coolant to a vehicle.
It is a further object of the invention to provide a variable area ram air inlet for a vehicle having minimum drag associated with the inlet.
It is another object of the invention to provide a variable area inlet for conducting ram air to a vehicle to minimize thermal cycling to the heat generating component within the vehicle.
It is a further object of the invention to provide a variable area ram air inlet for a vehicle for minimizing the inlet area over all vehicle speeds and ambient air temperatures while providing sufficient air for forced convective cooling to heat generating components within the vehicle.
It is another object of the invention to provide a variable area ram air inlet for a vehicle in order to optimize inlet air flow for diverse or variable velocity and environmental conditions.
These and other objects of the invention will become apparent as a detailed description of representative embodiments of the invention proceeds.